U.S. patent number 4,657,666 [Application Number 06/759,917] was granted by the patent office on 1987-04-14 for magnetic flotation.
This patent grant is currently assigned to W.S.R. Pty. Ltd.. Invention is credited to Terence C. Hughes, Harvey Snook.
United States Patent |
4,657,666 |
Snook , et al. |
April 14, 1987 |
Magnetic flotation
Abstract
A method for mineral upgrading or concentration, characterized
in that a gangue-associated mineral having a hydrophobic surface
and being in particulate form, is contacted with particles of a
magnetic material also having a hydrophobic surface, whereby the
mineral particles become attached to the surface of the magnetic
particles, the magnetic particles with the attached mineral
particles are separated from the gangue by magnetic means, and the
mineral particles are then detached from the magnetic
particles.
Inventors: |
Snook; Harvey (Aspendale,
AU), Hughes; Terence C. (North Carlton,
AU) |
Assignee: |
W.S.R. Pty. Ltd.
(AU)
|
Family
ID: |
3769249 |
Appl.
No.: |
06/759,917 |
Filed: |
July 29, 1985 |
PCT
Filed: |
October 26, 1982 |
PCT No.: |
PCT/AU82/00174 |
371
Date: |
June 07, 1983 |
102(e)
Date: |
June 07, 1983 |
PCT
Pub. No.: |
WO83/01397 |
PCT
Pub. Date: |
April 28, 1983 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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511136 |
Jun 7, 1983 |
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Foreign Application Priority Data
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Oct 26, 1981 [AU] |
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PF1302/81 |
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Current U.S.
Class: |
209/8; 209/47;
209/9; 209/214 |
Current CPC
Class: |
B03C
1/01 (20130101) |
Current International
Class: |
B03C
1/01 (20060101); B03C 1/005 (20060101); B03G
001/00 () |
Field of
Search: |
;209/3,4,5,8,9,47,39,166,214,232 ;210/222 ;232/49.6 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hart; Charles
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak, and
Seas
Parent Case Text
This is a continuation of application Ser. No. 511,136, filed June
7, 1983 and now abandoned.
Claims
What is claimed is:
1. A method for mineral upgrading or concentration comprising the
following steps:
providing a gangue associated mineral having a hydrophobic surface
and in particulate form,
providing a magnetic material in particulate form,
silanizing the magnetic material in order to provide a hydrophobic
surface,
contacting the gangue associated mineral with the magnetic material
in an aqueous liquid, whereby the mineral particles become attached
to the surface of the magnetic particles by virtue of interaction
between the hydrophobic surfaces of the particles,
separating the magnetic particles with attached mineral particles
from gangue by magnetic means,
detaching the mineral particles from the magnetic particles.
2. A method as claimed in claim 1, characterised in that the
particles are contacted by mixing in an aqueous liquid.
3. A method as claimed in claim 1 or claim 2, characterised in that
the magnetic material has been silanized to provide the hydrophobic
surface.
4. A method as claimed in claim 1, characterised in that the
mineral particles are rendered hydrophobic by treatment with a
flotation reagent and the magnetic material has been silanized to
provide the hydrophobic surface.
5. A method as claimed in claim 4, characterised in that the
mineral particles are detached from the magnetic particles after
separation by destruction of the flotation reagent.
6. A method as claimed in claim 1, characterised in that the
particle size of the magnetic material is at least comparable with
that of the mineral.
7. A method as claimed in claim 1, wherein the magnetic material is
magnetite, haematite, ilmenite, a ferrite or a magnetic metal or
alloy.
Description
BACKGROUND OF THE INVENTION
This invention relates to mineral upgrading or concentration method
involving the use of magnetic particles having hydrophobic
surfaces, as extractants for minerals with hydrophobic surfaces or
especially surfaces made hydrophobic by the use of the reagents
normally used for air flotation concentration.
A considerable art has been developed to separate minerals from
associated gangue using air bubbles. Typically a collecting
reagent, such as sodium ethylxanthate, is added to an aqueous
suspension of a mineral, for example chalcopyrite containing a
silica gangue. The ethylxanthate ions are preferentially adsorbed
by the chalcopyrite. If small air bubbles are then made to contact
both silica and chalcopyrite particles, only the chalcopyrite
particles adhere and they can then be floated to the surface of the
suspension and separated by skimming the surface. The air bubbles
are attached to the mineral by the surface tension developed in the
ring where the mineral protrudes into the air bubbles. The air
bubbles have buoyancy which counteracts the gravitational force on
the particles of mineral thus allowing flotation to occur. In many
instances the bubbles must be stabilised with frothing agents to
maintain the bubble with particles on the surface for sufficient
time to permit skimming of the floated mineral particles.
SUMMARY OF THE INVENTION
This invention seeks to provide a concentration method which
resembles the art of flotation but uses hydrophobic magnetic
particles instead of air bubbles as the separating medium. The
invention also aims to provide a method of mineral concentration
which represents an improvement over the use of air bubbles.
According to the present invention there is provided a method for
mineral upgrading or concentration wherein a gangue-associated
mineral having a hydrophobic surface and being in particulate form,
is contacted with particles of a magnetic material also having a
hydrophobic surface, whereby the mineral particles become attached
to the surface of the magnetic particles, the magnetic particles
with the attached mineral particles are separated from the gangue
by magnetic means, and the mineral particles are then detached from
the magnetic particles.
DETAILED DESCRIPTION OF THE INVENTION
Contact of the mineral to the magnetic particles may be carried out
by mixing the particles in a fluid, preferably aqueous liquid,
suspension, or the particles may be mixed together in the dry
state.
Generally, the mineral particles will require pre-treatment to
provide the necessary hydrophobic surface. Any of the known
reagents or treatment procedures used in conventional flotation
processes may be used for this purpose.
Although some suitable magnetic materials, such as for example,
magnetite, are known to have naturally hydrophobic surfaces and it
will usually be necessary to treat the magnetic materials to
provide a surface having the desired level of hydrophobicity.
All the currently known magnetic materials can be made hydrophobic.
In general, the magnetic oxide materials such as magnetite,
haematite, ilmenite, and the ferrites, can be activated by either
concentrated acid or alkali to give a surface rich in hydroxyl
radicals that can be used to attach alkyl silane or alkyl siloxane
and other organic reagents by methods known per se to produce
hydrophobic surfaces. Magnetic metals, such as iron, nickel, cobalt
and their alloys, e.g., alloys of rare earth elements and cobalt,
can be made hydrophobic by producing either hydroxyl-rich surfaces
in weak alkaline solutions or by generating a thin glass layer on
their surface and then further treating the surface with alkyl
silanes, alkyl siloxanes and like organic reagents.
The concentrated mineral particles may be detached from the
magnetic particles by any suitable method. For example, the
flotation reagent may be destroyed with oxidising reagents such as
hypochlorite, hydrogen peroxide or air, or by pyrolitic
degradation. Alternatively, the flotation reagent may be displaced
by ions such as cyanide or hydroxide. Detachment may also be
achieved mechanically, i.e., by violent agitation, for example that
caused by intense oscillating magnetic field.
Separation of the mixed mineral/magnetic particles from the gangue
and separation of the magnetic particles from the mineral particles
after detachment may be achieved by any suitable magnetic
separation apparatus of conventional or specifically-designed
type.
The optimum size for the magnetic particles for any particular
application will be best determined by experiment. Generally the
magnetic particles should be at least comparable in size with the
mineral particles and preferably somewhat larger. We have found
that for most applications involving mineral particles of 100 mesh
BSS or smaller magnetite particles of -60 to +100 mesh are most
suitable.
The method of the invention is very suitable for the upgrading of
slimes and sludges containing very fine mineral particles, e.g.,
those unamenable to concentration by flotation techniques.
The method of the invention also has other advantages. Firstly, the
mineral particles are attached to the magnetic particles by both
the forces of surface tension and also the considerable van der
Waals forces between the hydrophobic molecules on the magnetic
particles and the flotation reagent molecules on the mineral
particles. These forces when combined enable larger mineral
particles to be separated more reliably. When very fine mineral
particles are floated, the hydrophobic surfaces exert a powerful
force on miscelles of mineral by spreading them over the active
surface. The effect can be increased by using magnetic particles
with indented surfaces which allow increased area of contact and an
increased resolved surface tension force towards the magnetic
particles.
Secondly, the energy required to separate a magnetic particle using
a conventional magnetic separator is much less than the energy
required to compress air to make bubbles and then skim the
surface.
Thirdly, the magnetic flotation does not require frothing reagents,
which constitute roughly ten per centum of the cost of running a
conventional flotation process.
The invention is illustrated by the following examples.
EXAMPLE 1
A sample of magnetite was screened and the size range -60 +100 mesh
BSS retained for silanizing. The surface was cleaned with 1% sodium
EDTA, which was adjusted to pH 10 with ammonia, then washed with
distilled water. The magnetite was dried at 100.degree. C. and when
cool, a 30 gram sample was taken and stirred into a 1% solution of
Dow Corning Z-6020 silane
(N-.beta.-aminoethyl-.gamma.-aminopropyltrimethoxysilane) then
decanted to remove excess reagent. The reaction was completed by
drying the treated magnetite at 100.degree. C. for 2 hours.
10 g of molybdenite ore from Everton, Victoria, passing 50 mesh BSS
was ground under nitrogen into a surface-activating solution of 1%
sodium ethylxanthate and 0.25% sodium cyanide adjusted to pH 8-9.
Excess reagent was removed by decantation. 5 g of the silanised
magnetite in 100 ml of water was then mixed into the activated ore
with gentle stirring for 10 minutes under nitrogen, then recovered
by magnetically removing the magnetite (with attached molybdenite)
upwards out of the solution with a magnet, and dried to give 4.1 g.
The molybdenite was then recovered by treatment with 20 ml of 50
vol. hydrogen peroxide for 10 minutes followed by agitation and
magnetic removal of the magnetite to leave concentrated molybdenite
which when dried was found to weigh 1.4 g. Analysis showed a 6.2:1
concentration of molybdenite from the ore to the concentrate.
EXAMPLES 2-4
Using the method of Example 1, the following ores were concentrated
as tabulated below.
______________________________________ Metal/Concentration Example
Ore achieved ______________________________________ 2 Pyrite.sup.1
Fe 5.1:1 3 Chalcopyrite.sup.2 Cu 6.7:1 Fe 8.1:1 4 Lead/zinc.sup.3
Pb 4.0:1 Zn 5.1:1 ______________________________________ .sup.1
From Broken Hill, NSW, Australia .sup.2 From Mt. Lyle, Tasmania
.sup.3 Freshly-mined high grade ore from Broken Hill, NSW,
Australia
EXAMPLE 5
The use of haematite instead of magnetite in the above experiments
gave similar results to those stated, the only major difference
being that a more powerful magnet was required to lift the material
out of the suspension.
50 g of a screened sample of haematite (-100+120 mesh BSS) was
heated at about 700.degree. C. for 2-3 hours in a nickel crucible
which was flushed with nitrogen. The crucible was covered and
removed from the furnace and the contents poured into 100 ml of
absolute alcohol containing 0.5 ml of glacial acetic acid. Z-6020
silane (1 ml) was added with stirring and the mixture was then
stirred for 5-10 minutes, decanted, and the solid washed with
distilled water and dried at about 120.degree. C. for 2 hours.
Using the lead/zinc ore of Example 4, the concentrations achieved
were Pb 5.0:1; Zn 4.5:1.
* * * * *